Garlic: a new flavor of federated query processing for DB2

In a large modern enterprise, information is almost inevitably distributed among several database management systems. Despite considerable attention from the research community, relatively few commercial systems have attempted to address this issue. This paper describes new technology that enables clients of IBM's DB2 Universal Database to access the data and specialized computational capabilities of a wide range of non-relational data sources. This technology, based on the Garlic prototype developed at the Almaden Research Center, complements and extends DB2's existing ability to federate relational data sources.The paper focuses on three topics. Firstly, we show how the DB2 catalogs are used as an extensible repository for the metadata needed to access remotely-stored information. Secondly, we describe how the Garlic approach to query planning, in which source-specific modules and the federated server cooperate to develop an optimized execution plan, has been realized in DB2. Lastly, we describe how DB2's query execution engine has been extended to support queries and functions that are evaluated remotely.